The invention relates to vacuum boosters for motor vehicles. More particularly, the present invention relates to a rear bearing for a vacuum booster or power brake.
Power boosters operating on a pressure differential, such as exists between the engine intake manifold of a vehicle and the atmosphere, are well known devices. In the case of a single stage power booster, a shell-like housing typically encloses at least one variable pressure chamber that is separated from a vacuum chamber by a diaphragm and its supporting wall. The diaphragm and supporting wall are axially movable relative to the housing under variable pressure conditions. In order to achieve an increased boost effect, tandem power boosters have the interior of the housing subdivided by a housing divider wall separating a secondary variable pressure and vacuum chamber combination from the primary chamber pair. In all cases, a power piston is urged to move axially by the diaphragm(s) and actuates an output rod for operating the vehicle brakes through an engaged hydraulic master cylinder.
The master cylinder typically has bypass holes that must be covered, normally by primary and secondary seals, in order to develop hydraulic pressure in the brake line. To accommodate dimensional tolerances, the seals are usually situated some distance from the bypass holes. This distance gives rise to some travel in the vehicle brake pedal, which may be magnified by the remainder of the power booster.
The present invention is a power booster comprising a rear housing section and a power piston. An inner bearing is disposed around the power piston, and is adjustable relative to the rear housing section to translate the power piston.
Accordingly, it is an object of the present invention to provide a unique method of setting an axial dimension on a vacuum booster and/or adjusting a power brake.
Another object of the present invention is to provide a power booster of the type described above that reduces travel loss while the assembly is still in the assembly plant.
Still another object of the present invention is to provide a power booster of the type described above that reduces initial travel loss at the vehicle pedal.
Still another object of the present invention is to provide a power booster of the type described above that minimizes or avoids any need to adjust the end fitting of the output rod before attachment to the master cylinder.
These and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiment, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.